Abstract Rationale Exposure to second-hand smoking (SHS) has been associated with childhood asthma, a heterogeneous syndrome comprising unique mechanisms or endotypes. To date, little is known about the relation between exposure to SHS and asthma endotypes in children. This study aimed to evaluate the association between exposure to SHS during early life and/or school age and asthma endotypes and lung function in Puerto Rican youth, a group disproportionately affected with asthma. Methods Longitudinal study of 337 Puerto Rican Youth who completed a first study visit at ages 6-14 years and a second study visit at ages 9 to 20 years, approximately 5.3 years apart. Exposure to SHS was defined as exposure in early life (during pregnancy or the first two years of life) only, exposure at either study visit (at school age) only, or exposure in both early life and at least one study visit (at school age). Based on nasal epithelial expression of 8 “signature genes” for T helper (T)2 and T17 immunity, 3 asthma endotypes were identified at the second visit: T2-high, T17-high, and T2-low/T17-low. Percent (%) predicted values for lung function measures were calculated by the Global Lung Function Initiative 2021 race neutral equations. Multivariable regression was used for the analysis of exposure to SHS and asthma endotypes and lung function. Results Adjusting for age, sex, parental history of asthma, private or employer-based health insurance, persistent overweight or obese, annual mean level of PM2.5 prior the second visit, and time interval between study visits, those who were exposed to SHS both in early life and at school age had a 2.18 times higher odds of T17-high asthma (adjusted odds ratio aOR= 2.18, 95% confidence interval CI=1.01-4.71) and 2.61 times higher odds of T2-low/T17-low asthma (aOR=2.61, 95% CI = 1.15-5.91) as compared to those never exposed to SHS. Among participants who had T2-low/T17-low asthma, those who were exposed to SHS both in early life and at school age had 6.6% to 13.7% significantly lower %predicted FEV1 and %predicted FEV1/FVC as compared to those never exposed to SHS (see Figure). Conclusions In a study of Puerto Rican youths, exposure to SHS both in early life and school age were associated with an increased odds of T17-high and T2-low/T17-high asthma and lower lung function measures in participants with T2-low/T17-high asthma. This abstract is funded by: NIH
Pereira et al. (Fri,) studied this question.